code: def test_onnx_symbolic_raises_warning_when_overriding_function(self):
      self.assertFalse(
          registration.registry.is_registered_op("test::test_op", 9)
      )
  
      @registration.onnx_symbolic("test::test_op", opset=9)
      def test1():
          return
  
      with self.assertWarnsRegex(
          errors.OnnxExporterWarning,
          "Symbolic function 'test::test_op' already registered",
      ):
  
          @registration.onnx_symbolic("test::test_op", opset=9)
          def test2():
              return
  
imports: from typing import Sequence
  from torch.onnx import errors
  from torch.onnx._internal import registration
  from torch.testing._internal import common_utils
label_desc: Use image node_id 4 for calling the TestRegistrationDecorators obj's underlying member method code with example usage: obj.test_onnx_symbolic_raises_warning_when_overriding_function() without return types